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United States Patent |
5,074,490
|
Muse
,   et al.
|
December 24, 1991
|
Carrier tracking system
Abstract
An infrared tracker for tracking a carrier in clutter comprises a
pyrotechnically heated emitter, a beam concentrator, and a blanking means
all of which are mounted on the carrier, and a command link, a thermal
detector, a display signal storage means, a display, and a comparator all
of which are located remotely to the carrier, said command link operative
to provide an emitter start-up signal and a blanking command signal, said
emitter and blanking means operative in response to the command signals
sent to the carrier when there is clutter present that might be confused
with the carrier, respectively, to actuate the emitter and blanking means,
said display storage means operative to store a first video frame of the
carrier while the emitter is blanked out, and said comparator for
ocmparing the first video frame without the emitter to a subsequent video
frame including the emitter to distinguish between the clutter is being
substantially canceled.
Inventors:
|
Muse; Charles B. (Dallas, TX);
Colson; Kenneth K. (Dallas, TX);
Markle; Jack R. (Tucson, AZ);
LeCompte; George W. (Tucson, AZ);
Whipps; Patrick A. (Palmdale, CA)
|
Assignee:
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Texas Instruments Incorporated (Dallas, TX);
Hughes Aircraft Company (Los Angeles, CA)
|
Appl. No.:
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649270 |
Filed:
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January 30, 1991 |
Current U.S. Class: |
244/3.11; 244/3.12; 244/3.13; 250/495.1; 250/504R |
Intern'l Class: |
F41G 007/00; G21G 004/00 |
Field of Search: |
244/3.11,3.12,3.13,3.16
250/495.1,504 R
|
References Cited
U.S. Patent Documents
Re33287 | Aug., 1990 | Allen | 244/3.
|
3227879 | Jan., 1966 | Blau et al. | 250/495.
|
3275829 | Sep., 1966 | McClune et al. | 250/493.
|
3711046 | Jan., 1973 | Barhydt | 244/3.
|
3796396 | Mar., 1974 | Crovella | 244/3.
|
3797395 | Mar., 1974 | Tyroler | 250/495.
|
4001588 | Jan., 1977 | Elsner | 250/493.
|
4406429 | Sep., 1983 | Allen | 244/3.
|
4666103 | May., 1987 | Allen | 244/3.
|
Primary Examiner: Buczinski; Stephen C.
Attorney, Agent or Firm: Grossman; Rene E., Sharp; Melvin
Parent Case Text
This application is a continuation of application Ser. No. 456,188, filed
Dec. 15, 1989, which is a continuation of Ser. No. 126,800, filed Mar. 3,
1980, both abandoned.
Claims
What is claimed is:
1. A carrier tracking system having a beacon system including a beacon
subsystem mounted on the carrier and a beacon detector and control
subsystem positioned off the carrier, said beacon subsystem comprising a
housing having an open end, a pyrotechnic heater mounted in the housing,
an igniter means for igniting the heater, an apertured guide member
covering a major surface of the heater, and an aperture sheet movably
mounted relative to said apertured guide member for selectively covering
the apertured guide member.
2. A carrier tracking system according to claim 1 wherein the beacon
subsystem further includes an apertured honeycomb member mounted above the
aperture sheet with its apertures aligned with the apertures of the
apertured guide member.
3. A carrier tracking system according to claim 2 wherein the honeycomb
walls forming the apertures extend angularly outwardly from one major
surface to an opposing major surface.
4. A carrier tracking system according to claim 3 wherein the surface of
the honeycomb aperture forming walls are coated with a reflective
material.
5. A carrier tracking system according to claim 4 wherein the reflective
material is taken from the group consisting of gold and nickel.
6. A carrier tracking system according to claim 1 wherein the beacon
subsystem further includes a protective cover hermetically enclosing the
pyrotechnic heater.
7. A carrier tracking system according to claim 1 wherein the beacon
subsystem further includes a frangible glass cover attached to the open
end of the housing for closing the housing.
8. A carrier tracking system according to claim 1 wherein the beacon
subsystem further includes an insulating layer for insulating the
pyrotechnic heater from the housing.
9. A carrier tracking system having a beacon system including a beacon
subsystem mounted on the carrier and a beacon detector and control
subsystem positioned off the carrier, said beacon subsystem comprising:
a housing having an open end, a heat source mounted in said housing, an
apertured member covering a major surface of said heat source, and a
shutter for selectively obscuring said aperture member.
10. A carrier tracking system according to claim 9 wherein said heat source
is a pyrotechnic heater.
11. A carrier tracking system according to claim 10 further including an
igniter means for igniting said heater.
12. A carrier tracking system according to claim 9 wherein said shutter is
an apertured sheet movably mounted relative to said aperture member.
13. A carrier tracking system according to claim 12 further including a
shutter electronics to move said apertured sheet relative to said aperture
member.
14. A carrier tracking system according to claim 9 wherein the beacon
subsystem further includes an apertured honeycomb member mounted above
said shutter with its apertures aligned with the apertures of said
apertured member.
15. A carrier tracking system according to claim 14 wherein the honeycomb
walls forming the apertures extend angularly outwardly from one major
surface to an opposing major surface.
16. A carrier tracking system according to claim 15 wherein the surfaces of
the honeycomb aperture forming walls are coated with a reflective
material.
17. A carrier tracking system according to claim 16 wherein the reflective
material is taken from the group consisting of gold and nickel.
18. A carrier tracking system according to claim 10 wherein the beacon
subsystem further includes a protective cover hermetically enclosing said
pyrotechnic heater.
19. A carrier tracking system according to claim 9 wherein the beacon
subsystem further includes a frangible glass cover attached to the open
end of the housing for closing the housing.
20. A carrier tracking system according to claim 9 wherein the beacon
subsystem further includes an insulating layer for insulating said heat
source from the housing.
Description
This invention relates to an infrared carrier tracking, and more
particularly to a system for tracking the carrier through clutter.
In the past guidance techniques, such as those disclosed in U.S. patent
application, Ser. No. 896,087, filed Apr. 13, 1978 for a "Missile
Detecting and Tracking Unit" have provided some clutter immunity as
follows. During the early portion of the carrier flight, the carrier
engine, if it has one and if not a beacon, is the brightest object in the
detector field of view; all clutter objects have less intense images. The
size and location of the clutter is stored so that it will not become
confused with the beacon during the latter portion of flight when the
carrier engine image is dim. In addition, a two dimension track gate is
placed about the carrier to gate out any clutter. The gate is made just
large enough to contain the portion of space into which the carrier is
moving; as the carrier moves away, the gate is narrowed to eliminate
widely scattered clutter. Nevertheless, when a moving carrier is tracked,
new clutter is brought into the field view. Further, aspect angles of the
clutter during the flight can change and clutter location can change due
to operator jitter.
Accordingly, it is an object of this invention to provide for reliable,
effective tracking of a carrier through clutter.
Another object of the invention is to provide a tracking system having a
heat source whose intensity is controllable at short range to avoid
blooming and to effect smoke penetration at long range.
Still another object of the invention is to provide a tracking system
having clutter cancellation while tracking the carrier.
Yet another object of the invention is to provide a tracking system whose
sub-system aboard the carrier is highly efficient and reliable, yet
economical to produce using mass production techniques.
Briefly stated the invention comprises a tracking system which includes a
beacon sub-system mounted upon a carrier, and a beacon control sub-system
located remotely to the carrier. When a clutter ambiguity enters the
field, the control sub-system sends a beacon interrupt signal to the
beacon sub-system to interrupt the beacon. The resulting video frame is
stored for comparison with a subsequent video frame taken with the beacon
emitting energy. The subsequent frame is compared with the previous frame
and the comparison reviewed to determine the location of the beacon. Any
clutter present will be in both frames; however, the beacon will be
present in only one frame. By this technique the clutter is differentiated
from the carrier.
The novel features characteristic of the embodiments of the invention may
best be understood by reference to the following detailed description when
read in conjunction with the accompanying drawings wherein;
FIG. 1 depicts the utilization of a combined infrared sight and tracker
unit;
FIG. 2 is an isometric view of the carrier including the beacon shutter
system;
FIG. 3 is an isometric view of the beacon shutter system;
FIG. 4 is an isometric view of the shutter drive having a portion of the
housing broken away to show more clearly the shutter drive mechanism;
FIG. 5 is a fragmentary cross sectional view of the thermal beacon taken
along line A--A of FIG. 3;
FIG. 6 is a schematic view of the shutter-signal separation circuit and
power driver of the shutter electronics;
FIG. 7 is a schematic of the beacon/carrier interface; and
FIG. 8 is a simplified flow diagram of the infrared sight and tracker unit.
For purposes of description and not by way of limitation the invention
shall be described in connection with a guided missile used as the
carrier. Such a guided missile is shown in FIG. 1 in which an infrared
sight and tracker unit 10 comprises a missile 12 which has been launched
from launcher 14 toward its destination or target 16. The target is shown
as a tank viewed through the visual sight. It could also have been viewed
through the infrared sight at the gunner's option. A beacon 18 is attached
to the aft end of the missile 12. The beacon 18 is a part of the beacon
system described hereinafter. A sighting means 20 which may be, for
example, a thermal night sight such as that manufactured by Texas
Instruments Incorporated under the designation AN/TAS4 Night Sight, is
attached to the launcher 14 for viewing and tracking the carrier 12. The
night sight is a forward looking infrared receiver and imaging device
which includes a linear array of infrared detectors for scanning a field
of view to detect the thermal energy emitted from the carrier's beacon.
The night sight is modified, as hereinafter described, to accommodate a
beacon control sub-system.
Each detector of the sighting means together with its preamplifier
constitutes a channel (not shown) connected to an electronics package 22.
A controller 24 controls the launching of the missile, activation of the
night sight infrared receiver and activation of the beacon tracker unit.
The electronics package 22 includes a microprocessor, which is preferably
a Texas Instruments Incorporated SBP9900 microprocessor, controlled by the
controller 24.
The carrier missile 12 (FIG. 2) includes a beacon system 26, a housing 28,
an electronics pad 30 attached to the housing, an umbilical connector 32,
and ballast 34 attached to the faring 36. The housing 28 has an aft end to
which the beacon system is attached and a body portion to which the
electronics pod 30 is attached. The electronics pod 30 contains the
electronics for the beacon system. The umbilical connector 32 connects the
electronics pod 30 to the beacon system 26. The ballast 34 attached to the
faring 36 is to maintain the center of gravity or balance of the carrier
owing to the weight of the beacon system.
Referring now to FIG. 3, the beacon system comprises a housing 38, a
pyrotechnic igniter 40, a squib hammer 42, a shutter actuator 44, shutter
drive linkage 46, a shutter return spring 48, installation hooks 50, and
an installation bracket 52. The housing 38 is attached to the missile
housing 28 (FIG. 2) by the bracket 52 and hooks 50. The housing 38
includes a case 54 having an open end covered by a frangible glass cover
56. The case 54 (FIG. 5) may be, for example, a cast carbon type case. The
frangible glass cover is shattered for removal by the squib hammer 42
(FIG. 3). A layer of non-combustible insulation material 58 (FIG. 5)
covers the bottom of the case. A pyrotechnic heater 60 is hermetically
sealed in foil 62 for protection during storage. The pyrotechnic heater
may be selected from the group of intermetallic reaction pyrotechnic
materials consisting of titanium boride, titanium boride plus titanium
carbide, titanium carbide, zirconium boride, and zirconium carbide. The
foil 62 is a heat meltable foil which melts when the pyrotechnic heater is
ignited thereby enhancing the thermal path to an emitter 64. The emitter
64 is, for example, a carbon type emitter capable of withstanding the high
temperature (3800.degree. C.) effects.
An apertured base plate 66 covers the emitter 64. An apertured sheet 68 is
slidably mounted in base plate guides between the apertured base place
plate 66 and an apertured honeycomb optics 70. The aperture sheet 68 acts
as a shutter for obscuring the apertures of the base plate 66 and
honeycomb optics 70, which are in alignment, when displaced by about 1/2
the hole spacing. The apertured sheet or shutter 68 has two flexures 48
and 74 at opposite ends (FIG. 4). Flexure 48 acts as a return spring to
hold the shutter 68 open, i.e. the aperture sheet holes are aligned with
those of the base plate and honeycomb optics. Flexure 74 acts as a
transfer lever to the drive linkage 46.
The drive linkage 46 includes a rod 76 having, for example, ball shaped
ends. The ball shaped ends of rod 76 extend, respectively, through slots
in flexure 74 and one arm of a slotted flexure-pivoted bell crank 78. The
other arm o f the flexure-pivoted bell crank is attached to the core 79 of
a linear solenoid comprising the shutter actuator 44. Thus, with the
return spring 48 pulling the aperture sheet and the linear solenoid
pulling the shutter drive linkage to close it the system always acts in
tension thereby utilizing the tensile strength of the member to
substantially reduce the size of the members.
The shutter electronics 30 (FIG. 2) comprises a shutter-signal separation
circuit and power driver packaged separately from the beacon to fit the
available space and reduce mass unbalance in the missile. A power source
such as, for example, the existing missile battery 80 (FIG. 6) provides
power to a dc regulator 82 and power driver 84. The dc regulator provides
selected dc voltages to a buffer amplifier 86, 2-pole low pass filter 88
and threshold detector 90. The buffer amplifier 86 reestablishes the
values of the guidance and beacon actuator signals received by the
missile. The two-pole, low pass filter, with a preselected corner
frequency rejects the missile steering commands and passes the shutter
actuating dc pulse. The dc shutter pulse signal triggers a threshold
detector 90 which drives the power driver output stage 84. The power
driver contact is connected to the shutter actuator 44 solenoid (FIG. 3 &
4). The command pulse duration is selected to keep the shutter closed for
an interval equal to one time frame of the night sight.
The beacon/missile interface electronics (FIG. 7) comprises the power
source 80 which is connected to the junction of the shutter drive
electronics pod 30, fusible link 92 of a pyrotechnic initiator branch
circuit, and switch 94 of a squib hammer branch circuit. The pyrotechnic
initiator branch circuit, in addition to the fusible link 92 includes a
pyrotechnic initiator 96, which is, for example, an electrically fired
heat match. The squib hammer branch circuit includes, in addition to the
switch 94, a fusible link 98 connected to the switch 94 and to a squib
100. The fusible links 92 and 98 are included in the heater ignition and
cover removal circuits to protect the battery from potential overloading.
At start up, the squib of the squib hammer circuit is fired electrically
and the gas generated drives the hammer 102 which is a low brisance
pyrotechnic hammer. The cover 56 being a chemically tempered glass having
a thickness of about 0.050 to 0.060 inch and a modulus of rupture of about
40,000 psi. is fragmented and removed by the hammer within about 10
milliseconds. Also at start up the beacon or heater is fired. The heater
pyrotechnic has a propogation velocity such that the time for the reaction
to spread to the entire source is comparable to the missile's flight time.
Thus, the emitter 64 (FIG. 5) first meets the need for lower intensity
early in flight and is gradually raised throughout the flight to meet the
hither intensity need during the later stages of flight.
As previously described the shutter drive electronics 30 (FIG. 2) controls
the actuation of the shutter actuator 44 solenoid (FIG. 3). Standby power
for the shutter electronics 30 is low (about 1 watt). When shutter
operation is commanded, each cycle draws up to about 10 watt-seconds.
Shutter operation, if it occurs at all, will happen near the end of the
flight. The microprocessor of the electronics package 22 (FIG. 1) is
programmed (FIG. 8) so that upon receipt of a start up signal 104 tracker
conditioning 106 is effected by starting the clock, timing sequence and
determining pre-fire conditions. A time decision 108 is then made. If the
time is less than a preselected time, a decision 110 is made whether the
tracker is in handoff. Handoff results when the tracker looses the
missile. If the answer is no the computer commands the missile to fly a
standard track link 112, and the computer returns 114 to start 104. If the
tracker is in handoff, a decision 116 is made whether the missile is in
the field of view of the forward looking infrared (FLIR) sight. If not, a
command 118 is given for the missile to fly a preprogrammed flight
profile. Next a command 120 is given to activate a GLI tracker for missile
acquisition and the computer returns 122 to start 104. If the missile is
in the field of view a command 124 is given to compute the centroid area
of the last field and based thereon to compute a position estimate. The
computer then returns 126 to start.
When the decision 108 is that the preselected time has been reached,
commands 128 and 130 are given to establish, respectively, scene
stabilization and a peak set. Next a command 132 is given to establish a
clutter map reference from the stabilized scene. Then a command 134 is
given to reject peaks in the clutter maps by comparing the established
peaks with the clutter map reference. Next a command 136 is given to
update the clutter map. Then a decision 138 is made whether any peak
remains. If no peak remains a command 140 is given for the tracker to
coast and then return 142 to start 104. If yes, a decision 144 is made
whether more than one peak exists within a reasonable radius of the
previous missile track. If only one peak exists, a command 146 is given to
compute the centroid area which is converted to guidance signals. Then the
computer returns 148 to start. If more than one peak exists, a command 150
is given to actuate the beacon shutter system, and the beacon shutter 68
is closed for one video frame. All peaks appearing in the map during this
frame are known to be clutter and are entered in the clutter map. The
beacon is then turned on again and the computer returned 152 to the start.
Although only a single embodiment of this invention has been described
herein, it will be apparent to one skilled in the art that various
modifications to the details of construction shown and described such as
for example, substituting a laser (CO2 laser) for the pyrotechnic, may be
made without departing from the scope of the invention.
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